Energy-based debounce of mode shift frequency for optimization-based hybrid vehicle control strategies

Abstract

Solving the optimal control problem within optimization-based hybrid control strategies usually leads to high frequency changes between driving modes. Depending on the powertrain configuration, these mode shifts can simply mean activation and deactivation of the internal combustion engine (ICE), switching between different hybrid modes, e.g. series and parallel driving or even gear selection. Especially under dynamic as well as real driving conditions any kind of post-processing is very likely required for limitation of this frequency due to drivability reasons. Most commonly used are time domain filters, hystereses or penalty terms. Nevertheless, these post-processing methods affect the fuel efficiency of the control strategy itself and do not achieve optimal behaviour under all circumstances. Therefore, in this paper, a new possibility for debounce of mode shifts has been investigated using dynamic longitudinal vehicle simulation. By including a physical transition cost vs. benefit estimation for each possible shift in driving mode an energy-based debounce method can be set up. The proposed method enables further improvements towards optimal control. The debounce approach itself requires no predictive knowledge. Recently, both drivability and efficiency can be obtained simultaneously and even for customer use.